Human beings spend roughly one-third of their life sleeping. Studies show that a good night's sleep (usually seven to nine hours) promotes a sense of well-being, and that sleeplessness leaves us feeling exhausted, irritable and easily overwhelmed by the day's challenges. Not surprisingly, sleep consistently ranks in surveys as one of life's most pleasurable activities. However, the percentage of both U.S. men and women in all age groups who are chronically sleep-deprived, averaging six hours of sleep or less, has risen significantly in recent decades, according to the Centers for Disease Control and Prevention.

Among the causes are societal shifts, like longer work hours and shift work, greater emphasis on getting ahead and increased technologies. But it's a worrisome trend. Studies have shown that insufficient or mistimed sleep can contribute to serious health problems, such as cardiovascular disease, obesity, diabetes, depression and cancer, as well as auto accidents.

About 30 percent of the adult population suffers from insomnia—difficulty falling or staying asleep—and in a recent national survey, one in three adults reported difficulties related to sleep loss, such as trouble concentrating or remembering.

Sleep disturbance can also be a symptom of other medical conditions, like chronic pain, breathing disorders or psychiatric problems. But when such medical conditions are not the cause, sleep problems are commonly rooted in simple poor habits.

GET IN RHYTHM

Sleep is a 24-hour (circadian) rhythm generated by the brain's biological clock. Getting up every day at about the same hour keeps your internal clock set to local time and promotes getting sleepy at roughly the same time each night. Keeping this clock synchronized is simple: develop a relaxing pre-bedtime routine (like bathing and reading), and keep the bedroom quiet, dark, cool and reserved just for sleep (and sex). Performing work, playing videogames and other waking activities in bed are cues to stay alert, not to go to sleep.

Be aware that not everyone needs eight hours of sleep; we need just enough to feel rested and to function well. Avoiding naps is helpful, but if you must, nap early in the day and keep it short, under 20 minutes. And because the brain's clock is set by environmental lighting, exposure to bright outdoor light early in the day helps the clock maintain a healthy alignment and eases troubles falling asleep at bedtime.

WATCH WHAT YOU EAT (AND DRINK)

Avoiding substances known to disturb sleep is another basic tenet of good sleep hygiene. Caffeine has a longer action in the body than most people realize (the half-life, or time for the body to eliminate half the amount imbibed, is typically five to 10 hours), so it can contribute to trouble staying asleep as well as to bedtime insomnia. Limit caffeine to the first thing in the morning, and don't overdo it. Other stimulants, like tobacco and chocolate, are also no-no's in the evening. And while many people look to alcohol, a central nervous-system depressant, for help in falling asleep, once metabolized it promotes rebound sleeplessness later in the night.

Maintaining a healthy diet and body weight is also a foundation of healthy sleep, as weight gain promotes esophageal acid reflux, snoring, and stoppages of breathing called apneas, all of which cause awakenings. Avoiding meals near bedtime minimizes reflux, too, but if you need a late-night snack, stick with a combo of complex carbohydrates and protein, because that makes the sleep-promoting amino acid tryptophan more available to the brain.

Regular aerobic exercise not only keeps body weight in check (and reduces anxiety and depression), but also promotes sounder, deeper sleep. Though experts previously thought that exercise close to bedtime was too stimulating, the latest findings from the National Sleep Foundation reveal that some people benefit from exercise timed just before retiring.

CLEAR THE MIND

Stressful life events can cause insomnia, too—and insomnia itself can be a stress. If people become overly fixated on their inability to sleep, it can lead to hours in bed trying to force sleep to come, which, in turn, causes anxiety and arousal. Over time, this pattern can become ingrained, so that the insomnia persists long after the original stressor has passed. If you can't sleep, relocate to another room to do something relaxing, like reading, until you feel sleepy, and take to heart that you'll get back to sleeping better soon enough.

Not including over-the-counter sleeping pills, Americans received prescriptions for over 60 million hypnotic medications in 2011, according to IMS Health, which tracks healthcare statistics. Side effects of these sleeping pills include next-day drowsiness, dependence and loss of efficacy over time. Unnecessary pharmaceuticals also harm the environment, because after being excreted from the body they go to water-treatment plants ill-designed to remove them.

If a self-help approach doesn't do the trick, a sleep expert can guide you through a non-pharmacological program called cognitive behavioral therapy that studies show is as effective as prescription hypnotics in treating chronic insomnia.